Purification of crude esterification mixtures



J. F. OLIN Filed Nov. 15, `1938 FIL April 8, 1941.

PURIFIC'IIOIv 0F CRUDE ESTERIF'ICATIOH MIXTURES INVENTOR: JOHN P. OLmA BY 'hm a. oww

ATTORNEY denser to a decanter.

fraction from the esterication still takes placel Patented Apr. 8, 1941 rasant i azaasze f rumrrcs'rron or canna Es'rnamroa'rron mismas John F. Olin, Grosse Ile, Mich., assgnor to The 'harples Solvents Corporation, Philadelphia;

Application November 15, v1938, Serial No. 240,514

` 4 claims. (ci 2oz-.soi

.The present invention pertains to the separation of impurities from crude esters of nitric acid. It was conceived as a solution of problems encountered inthe practice of the process described inthe application of John F. Olin, Frederick- P. Fritsch. and Joseph J. Schaefer, Serial No. 225,908, filed August 2 0, 1938, for- Manufacture of .nitric acid esters, and can best be understood by consideration of the problems encountered in attempts to concentrate the crude esterication mixtures obtained in the practice of the process of that-application.

In the process of application Serial No. 225,908, the alcohol, acid and urea are continuously passed to an esteriflcation vessel, and partial light of, thev attached drawing', in which the single figure is. a flow sheet illustrating the practice of the process of the invention. While the invention is applicable to theseparation of various mixtures of alcohols and esters into their respective constituents, it can best be understood by reference to the separation of the constituents f of a particular mixture.

A mixture of amyl nitrate and amyl alcohol formed by the action o f 45% nitric acid upon the commercial mixture of amyl alcohols 4sold underthe trade name of Pentasol, possessing a esterication takes place in that vessel, together with passage overhead of an azeotropic mixture of the desired ester together with alcohol, water -and nitric acid. 'Ihis azeotropic mixture is passed through a condenser and from that con- Division of the overhead in the decanter, and an oil layer containing the desired ester contaminated .with varying quantities of alcohol, water and-acid separates as the lighter layer in the decanter,` while the alcohol is the heavier layer.

-In the case of ester'ica'tion to lproduce ethyl nitrate, only small quantities of ethyl alcohol 'remain in the oii layer, constituting the crude ester obtained inthe decanter, since ethyl alcohol is substantially soluble both in water and in aqueous nitric acid, and therefore has an ainity for the water phase in the decanter. This is not the case, however, .'in esterication topro# duce amyl nitrate, since amyl alcohol is much more soluble in amyl nitrate than in the aqueous phase separating as the heavy layer in the decanter.

As an example` of the nature of the problem solved, it may be pointed out that,in a typical operation, an esterication mixture containing only 66% of amyl nitrate may be economically treated to separate a commercially satisfactory amyl nitrate in the practice of the invention. f' Theobject of the present invention has been to obviate vthese diculties and to provide a process by which mixtures. of esters of nitric 'acid with the esteriiying alcohol may be -thoroughly and economically ,separated into their respective constituents.

The-mannerv inl which the objects of the invention has beenattained will be evident from consideration of the following description in lthe specific gravity of 0.910 and an approximate amyl nitrate concentration of 55%, is passed to-the storage vessel I0. This crude ester mixture is fed continuously into a mixer I2, and water is simultaneously fed to this mixer I2 from container Hat approximately four times the rate of passage of the crude ester to the mixer I2.

The mixer I2 is provided with, an agitator for thoroughly mixing the Water with the crude ester, and the mixture produced in mixer I2 is passed to decanter I3.

Water containing dissolved amyl alcohol and very small quantities oi amyl nitrate is removed as the heavier phase from the decanter I3 and the oil phase containing the amyl nitratev is passed to a second mixer. I4, where it is again mixed with four times its .volume of water, continuously supplied from tank II. The mixture from mixer Itisv continuously passed to decanter I5, where an aqueous layer consisting of amyl alcohol, water and a small amount of am'yl -nitrate is again removed, and the oil layer is passed to a third mixer I6, where it is again mixed with approximately four times its volume position of the amyl nitrate.

ofvwater. The aqueous phase of the mixture produced in mixer I6 is separated as the heavy phase from decanter ILandthe oil phase, containing amyl nitrate, a small amount of amyl alcoholand a small amount of water, is passed The column I8 is maintained at a temperature suilcient to pass overhead a mixture rich in amyl alcohol and containing amyl nitrate and some water, and it is preferably operated undersubatmospheric pressure in order to avoid decom- The mixtu` e is.

eraticns performed refiuxecl to column I8. 4The lower phase fromk decanter 2@ is sent to column 26 forstrippingv to separate its organic content from water. The

higher boiling components of the mixturepassed to column I8 accumulate in the still 2| and are pumped into column 2 2. This column is operated under a pressure suillciently low and a. temperature sumciently high tocause -amyl nitrate to in mixersfiz, u and is, instead of water.

Modifications will be o vious to those skilled in the art and I do not wish'to be the 'scope of the sub-joined claims.

1. A process oiobtaining a purined nitric acid ester from a crude esteriiication' obtained be passed overhead, andl this overhead fraction j is condensed in condenser 23, and passed thence to weir box 24, from which a part is reiluxed to column 22, while the remainder passes to receiver 25. The amyl nitrate so passed to receiver Zlis lof approximately 98% purity and has a specic gravity of 0.989.

The aqueous layers from decanters I3, I5, |`Iv and 20 are combined and passed to a column 26,

after addition oi small quantities oi' sodium carbonate from container l2 to neutralize the small quantity of free acid contained in these fractions. A mixture rich in amyl alcohol and water and containing buty small quantities' of amyl nitrate is passed overhead from column 26. This mixtureis condensed in condenser 21 and subjectedv to decantation in decanter 28.` The oil (upper) layer,y containing 88% .amyl alcohol, 5% amyl nitrate and '1% Water, is passed to receiver 29,

where it may be held i'or subsequent esteriflca` tion with further quantitiesiof nitric acid of between.40% and 50% concentration. The water (lower) layer, from decantr 2 8 is continuously relluxed to column 28 and is ultimately stripped of organic material. Water, collecting' in pot 3 0,

is discarded.

While the inventionhas been described above by esterifying nitric acid 'hol which is substantially `soluble in said ester'.-

ester,"said alcohol,` water by esterifying nitricacid with a' monohydric alcohol which is substantially soluble in said ester, and which contains said ester, said alcohol, water and at least a small amount. of nitric acid, said process comprising mixing with said ester a quantity of water which is substantiallyygrea'ter than the quantity ofsaid mixture under treatment, stratifying the resulting mixture of said crude esterincation mixture and added water to obtain a lighter stratum containing water, alcohol, and v a higher proportion of ester than said original mixture. and a heavier stratum containing water, alcohol and a smaller proportion oi.' ester than said original mixture, separating said strata from each other, the materials of said separated lighter stratum to recover purified nitric acid ester therefrom.

2. A process of obtaining afpuried nitric acid ester from a crude esteriiicati'on mixture obtained and which contains said and at least a' small amount of nitric, acid, said process comprising mixing with said ester a 'quantityof water which is substantially greater than with special reference'to an esteriilcation'mixture obtained by azeotropic esteriilcation of amyl alcohol, it is to be understood that the principles of the invention are applicable to the separation of mixtures of aloholsand nitric acid esters of aliphatic hydrocarbon compounds generally, no matter how these mixtures are produced.

In the above description, the invention has been discussed in connection with the use of water as the extracting solvent. It is to be yunderstood that the invention is notvlimited to the use of the quantityof said-mixture under treatment; stratifying the resulting mixture of said crude esteriilcation mixture and .water to obtainl a lighter stratum containing water,"'alcohol, anda higher proportion of ester than said original mix-' ture, and thereafter' distilling the materials of said lighter stratum to recover puried nitric acid ester therefrom.

v3. 'A process as deiix'ied in claim 2, in which the step of distillation is accomplished under subatmospheric pressure.

, 4. A process as defined in claim 2, in whic'h the distillation step is accomplished by passing overpure water,- since substance having selective Y solvent action upon? the alcohol content of the esteriiication mixture' and` capable ofbeing removed frorn that mixture by. decantation may be substituted for water in the `practice of the invention.- Thus, forexample, dilute nitric acid or sulfuric acid of varying 'concentrations may be used as the extraction solventl in the washing op-v head a mixture containing the alcohol, water and the nitric. acid ester, stratifying this overhead fraction to separate an aqueous phase from a phase rich in the organic constitu'nts, and thereafter returning material from saidpha'se-containing the organic constituents' to said distillation operation as redux. v

JOHN F. oLIN. A

limited except by.

and thereafter separately distilling 

